Semiconductor packages can include multiple semiconductor dice in a stacked configuration. One type of package, known as a "connector", has parallel spaced cavities wherein the dice are mounted. The package can be mounted to a supporting substrate, such as a printed circuit board, to form multi chip modules and other electronic assemblies. For example, memory modules can include multiple memory devices, such as DRAMs, housed in the same package.
With some packages, direct electrical connections can be made between the bond pads on the dice, and mating contacts on the supporting substrate. Alternately, the packages can include electrical members for contacting the dice and supporting substrate. One feature of most prior art semiconductor packages is that the electrical connections between the dice and packages, or between the dice and supporting substrates, are permanent connections. For example, the connections are typically bonded connections, such as reflowed solder, or a cured conductive adhesive material.
The permanent electrical connections make assembly and disassembly of the packages difficult. In particular, the permanent electrical connections permit the packages to be assembled and disassembled only by semiconductor and electronics manufacturers having specialized equipment. It would be advantageous for packages to be constructed to allow disassembly and re-assembly by other users of the packages, such as consumers. This would permit the dice in the packages to be removed and replaced as required. For example, packages used for computer memory modules could be upgraded by consumers using the latest memory devices to replace the original dice in the packages.
Another problem with conventional semiconductor packages is stress generated by thermal cycling. In particular, the coefficient of thermal expansion (CTE) for the dice is typically different than the CTE of the packages and supporting substrates. Accordingly, the dice can expand by a different amount, stressing the electrical connections. Solder electrical connections are particularly susceptible to cracking and separation. It would be advantageous to provide packages with non-bonded electrical connections. This would permit movement of the dice to absorb thermal stresses.
Another aspect of semiconductor packages is that dice are being manufactured with large numbers of bond pads (e.g., 50 or more) which provide increased input/output paths to the integrated circuits contained on the dice. This requires a large number of electrical connections and associated electrical paths to be made to the dice. Optimally, a semiconductor package is constructed to accommodate large numbers of device bond pads.
The present invention is directed to an improved semiconductor package which can be easily disassembled and re-assembled without special equipment. In addition, the package includes resilient non-bonded electrical connections, which facilitate disassembly and re-assembly, and which absorb thermal stresses. Still further, the package can accommodate dice having large numbers of bond pads.